1. Field of the Invention
Embodiments relate to a method and system to dynamically allocate a frequency to a femto terminal and a macro terminal based on a priority of quality of experience (QoE) to achieve load balancing and interference avoidance that may occur in a heterogeneous network.
2. Description of the Related Art
Locating a transmission end and a reception end to be adjacent to each other is most efficient to improve a capacity of a wireless communication system. A femtocell technology may be an efficient method capable of achieving effects in terms of cost.
The femtocell technology has potential advantages in view of expansion of indoor coverage, energy efficiency, and cost and thus, has been applied to a high speed wireless communication system. Also, a femtocell has been adopted as one of the principal functions of a long term evolution (LTE) system. An LTE femtocell may use all the bands defined in 3rd Generation Partnership Project (3GPP) and may not require an exclusive frequency band. However, due to such reasons, critical co-channel interference (CCI) may occur between a macrocell and a femtocell.
In detail, due to expendability, security, and the limited availability of a backhaul band, substantial interference issues may arise between two hierarchical networks. That is, in view of social communication based or spectrum availability, it may be more effective to use both a macrocell base station and a femtocell base station on the same spectrum. However, to this end, a channel needs to be shared between two hierarchies, which may cause serious interference in a shared channel. Recently, proposed are many methods for solving such interference that may occur in a network in which a femtocell and a macrocell coexist.
Meanwhile, major requirements for a macrocell may be to enable a user to perform communication without using a separate device at any time and at any place, or even during a travel. Many users may be provided with a communication service from each macrocell base station and thus, the communication capacity of the macrocell needs to be preferentially secured compared to the communication capacity of a femtocell. Although inter-layer interference is present against the femtocell, a minimum target signal-to-interference noise ratio (SINR) of a macrocell user may need to be satisfied.
To this end, an amount of power to be decreased at the femtocell needs to be known to satisfy a target SINR of the macrocell user. A relatively small amount of time needs to be used during a process of processing an interference mitigation/cancellation algorithm. Further, an interference mitigation/cancellation method having simple complexity is required to possibly minimize latency. Also, when performing interference mitigation/cancellation, a combination with another resource management is required, such as power and subchannel allocation.
As described above, a femtocell may need to be capable of performing a plurality of measurements in order to be provided with sufficient information for interference mitigation/cancellation between two hierarchical networks and at the same time, to maintain coverage of the femtocell.
For example, a current LTE technology report proposes a variety of options as to an information exchange method between a macrocell and a femtocell. For example, there are an information exchange method using direct broadcasting between a macrocell base station and a femtocell base station, an information exchange method using broadcasting between a macrocell base station and a femtocell base station through a user terminal, an information exchange method between a macrocell base station and a femtocell base station through an X2 based interface that is a signaling protocol between base stations, and an information exchange method between a macrocell base station and a femtocell base station and between femtocell base stations through an S1 based interface that is a signaling protocol between a base station and a gateway.
In this regard, Korean Laid-Open Publication No. 10-2009-0127908, titled “Method and apparatus for controlling interference of base station”, discloses a method and apparatus for controlling interference of a femtocell base station using an existing X2 interference control message, instead of newly defining an interference control message in an S1 interface, by converting, to a format based on a protocol of the S1 interface, an X2 interference control message used for an X2 interface and by transmitting the converted X2 interference control message through the SI interface, in order to control interference occurring in a femtocell environment in which the X2 interface is absent.